Should I use ANSI C (C89)?

Question

It's 2012. I'm writing some code in C. Should I be still be using C89? Are there still compilers that do not support C99?

I don't mind using /* */ instead of //.

I'm not sure about C89 forbids mixing declarations and code. I'm kind of leaning towards the idea that it's actually more readable to have all the declarations in one place, and if it isn't, the function is too long.

VLAs look useful but I haven't needed them yet.

Should I stick with C89 if I don't have a compelling reason not to? Are there other things I haven't considered?

Answer 1

Unless you know that you cannot use a C99-compatible compiler (the Visual Studio C compiler is the most prominent candidate) there is no good reason for not using the nice things C99 gives you.

However, even if you need to support that compiler you can use some C99 features - just not all of them.

One feature of C99 that is incredibly handy is being able to do for(int i = ...) instead of having to declare your loop variable on top of the function - especially since C actually has a block scope. That's the kind of declaration where having it on top really doesn't improve the readability.

Answer 2

There is a reason (or many) why C89 was superseded by C99. If you know for sure that no C99 compiler is available for your particular piece of work (unlikely unless you are stuck with Visual Studio which never supported C officially anyway), then you need to stay with C89 but otherwise you should certainly put yourself in a position where you can benefit from the last 20+ years of improvement. There is nothing inherently slower about C99.

Perhaps you should even consider looking at the newest C11 standard. There has been some important fixes for dealing with Unicode that any C programmer could benefit from (other changes in the standard are absolutely minimal)...